Install grub on your system ( just the package, or download and compile yourself ) Then login as root and type
It will take its time, while it tests the bios, now set the root to your /boot directory disk. say
Thats hdb2 I've set it too as an example. Now to install it to the the right place for your purpose type
Thats it. quit with the command quit.
You just have to write your menu.list, The GRUB manual
hass all the details you require.